This invention is directed to a process which provides high lube yields with substantially higher VI's than previously achieveable from inexpensive lower or light olefins such as propylene. More particularly, this invention is directed to a process wherein high VI lube oils are made from propylene containing feeds using ZSM-5 type catalysts wherein the surface activity of the catalyst has been modified by reducing or substantially eliminating the surface acidity.
The conversion of olefins over ZSM-5 type zeolites is known in the art and is the subject of many patents. For example, U.S. Pat. No. 4,227,992 and the patents mentioned therein are excellent examples of the prior art in connection with this general subject.
U.S. Pat. No. 4,126,644 discloses conversion of a C.sub.5 -400.degree. F. liquid fraction, from a Fischer Tropsch synthesis, prodominately C.sub.5 -C.sub.10 olefins over zeolite ZSM-5 in order to produce higher boiling products including a 650.degree. F.+ lube fraction.
U.S. Pat. No. 4,101,595, in a process for conversion of ethyl benzene to p-xylene discloses a dual functional zeolitic catalyst in which preferably the acid function activity is reduced, for example, by either pretreatment of the catalyst or by co-feed of an agent which impairs the acid function, e.g., ammonia, an amine, or other ammonia derived compound.
U.S. Pat. No. 4,100,215 and 4,002,697 disclose in selective p-xylene production the use of suitable compounds of nitrogen or silicon, preferably an organic radical substituted silane, to modify and deactive the external surface of a crystalline aluminosilicate zeolite catalyst.
Additionally, zeolites have been modified via exchange and similar technology with large cations such as N.sup.+, P.sup.+ large branch compounds such as polyamines and the like, see U.S. Pat. No. 4,101,595; large phenols and via silicating agents see U.S. Pat. Nos. 4,100,215 and 4,002,697, respectively.
It has now been discovered that the viscosity index of lubes produced from olefins such as propylene over zeolitic catalysts can be greatly improved, for example, by removing its surface acidity by treating the catalyst for example, with a bulky amine such as a disubstituted pyridine, e.g., 2,6-di-tertiary-butylpyridine. Either a one stage or a two stage process utilizing this concept can be used to provide high yields from the polymerization of lower olefins by catalysis with ZSM-5 type zeolites treated as described herein.